Hollow TiO2Spheres Effect on Dielectric Strength of Oil-Paper Composite Insulation

Dielectric strength of transformer oil and oil-impregnated paper has been widely investigated to ensure operation safety of power transformers and other electrical equipment. Addition of nanoparticles has exhibited the ability to improve insulation strength of oil or oil-impregnated paper. However, enhancement on breakdown strength of oil-paper composite insulation (OPCI) is still a challenge, especially under DC voltage. In this work, both solid and hollow TiO
₂
spheres were synthesized and added to transformer oil and oil-impregnated paper. DC breakdown voltages (DCBV) of OPCI before and after adding spheres indicates that modification effect of hollow spheres is superior to that of solid ones. After adding hollow spheres, the positive and negative DCBV of OPCI are increased to 1.42 times and 1.64 times of the positive DCBV of OPCI with solid spheres, respectively. Possible modification mechanism has been discussed and proposed based on further investigation of electric field distribution and interface-charge characteristic of OPCI with two kinds of spheres.